Doors of the type used for closing a large opening in a building, such as a garage door, have long been manufactured utilizing a plurality of substantially identical panels which are hingedly connected together to permit relative hinging movement between the adjacent panels when the door is being moved between a closed vertical position and an open horizontal position. Such multipanel doors, commonly referred to as sectional doors, often employ individual wooden panels which are appropriately hingedly connected at the adjacent horizontal eddges thereof. However, wooden panels are costly to manufacture and result in the door being extremely heavy, particularly when the door is of large size. The weight of such doors thus makes opening and closing of the door extremely difficult, even when an automatic operator is utilized.
In an effort to improve upon sectional doors, panels which are rolled or formed from a thin sheet material, such as metal, fiberglass or plastic, have been utilized. These rolled or formed panels are necessarily provided with some form of irregular cross-section, such as a channel shape, so as to provide the panels with increased strength and rigidity. However, such panels have still required the use of additional strengthening members in the form of end stiles which are normally secured to each panel along the vertically extending edges thereof. These panels are also normally provided with a rigid reinforcing member in the form of a center stile which is rigidly attached to the panel to improve the strength thereof. These end and center stiles, which all extend in the direction of the door height, have provided the door with substantial strength in the direction of height, while still resulting in a rather light weight yet strong door.
While doors using formed or rolled panels as described above have proven acceptable, and in fact desirable, in some use situations, nevertheless many doors constructed from such panels have proven undesirable in other use situations. Specifically, in situations where the door is of substantial width, it has been discovered that the door does not possess the necessary strength and rigidity along the width direction thereof so as to be capable of withstanding transverse loads of rather large magnitude, such as wind loads.
Particularly, the panels of these known sectional doors are commonly formed with a channel-like cross section which is necessarily of rather limited depth in relationship to the overall door thickness, such as a maximum of approximately 50% of the overall door thickness. Thus, even though such channel-shaped panels are provided for the purpose of increasing the strength of the door along the width direction thereof, nevertheless these channel-shaped panels have not imparted the required strength and rigidity in all use situations. Thus, where the door is extremely wide and a rather large wind load is imposed on the door, the wind load causes the center portion of the door to deflect inwardly, which in turn causes the edge portions of the door and the rollers mounted thereon to be withdrawn from the supporting tracks. Needless to say, this weakness in the door as viewed in the width direction thereof, which weakness permits sufficient deflection or bowing of the door to cause disengagement of the door rollers from the supporting tracks, is highly undesirable since it disrupts proper door operation and in some instances results in damage to the door and its related support structure.
Accordingly, the present invention relates to an improved sectional door which overcomes the above-mentioned disadvantages. Specifically, it is an object of the present invention to provide:
1. A sectional or multipanel door wherein the individual panels have a cross section of increased depth to provide the panels with increased strength, particularly in the longitudinal direction thereof, so that the door has substantially increased strength in the width direction thereof.
2. A door, as aforesaid, which utilizes panels having a channel-like center portion for strengthening the panels in the lengthwise direction thereof, which center portion has a depth which is at least approximately 75% and preferably approximately 80% of the door thickness to provide the panel with substantially increased strength and rigidity.
3. A door, as aforesaid, wherein the improved panel strength permits the assembled door to utilize end and center stiles of substantially reduced size and cross section.
4. A door, as aforesaid, which is capable of withstanding relatively large transverse loads, such as wind loads, even when the door is of substantial width.
5. A door, as aforesaid, which can be of lighter weight without sacrificing strength by providing increased strength due to the improved cross-sectional configuration of the individual panels.
6. A door, as aforesaid, which simplifies the production of the individual panels and permits a more efficient production of the assembled door.
Other objects and purposes of the invention will be apparent to persons acquainted with structures of this type upon reading the following specification and inspecting the accompanying drawings.